At WOT (or any speed for that matter) my Riviera goes through the gears no problem. However, when I put my foot down to the floor and shift into the passing gear, the car won't shift back out. Normally the car would shift around 70 mph however now it won't, it just sits there. If I pull my foot off the gas, it'll shift. Fluid levels are fine so I was thinking modulator valve. Anyother ideas?
You want to shift it manually, and the transmission is having none of that under WOT conditions. I don't think there is anything wrong. The transmission is getting 3 inputs, modulator, governor, and detent (kick down switch). Based on those 3 inputs, the valve body determines shift point. When you manually select the up shift, the transmission says no, I'll shift when I am ready:laugh: I am not a fan of manually shifting a street car. I like to set the governor so that the transmission shifts at the RPM I want at WOT. I feel this makes the car easier to drive hard, and more consistent. If you set the governor up, and your kick down system is working correctly, there isn't any room for improvement by shifting manually. Just my .02
Here is the heading: "Increased modulator pressure increases main-line pressure and tends to keep the shift valves in the downshifted position. Increasing governor pressure" http://books.google.ca/books?id=KKP...ition. • Increasing governor pressure&f=false I hope this helps. Chris
You must have misunderstood me, at no point did I say I was manually shifting the car. I put the car in drive. I punch the pedal. It shoots up to 70 mph no problem, shifting happily away. At 70 it wants to kick back down but something is holding it there, it can't and won't shift down. I take my foot off the gas for a moment. The tranny shifts, and life is good again. I'm thinking modulator valve, but do you have any other ideas?
You are right, I'm not understanding you, and I still don't. In your first post, you say you put your foot to the floor and shift into passing gear. I took that to mean that you manually shift it, and then tried to shift back up. Then above you say, it want to kick down, but something is holding it there, and it won't shift down. Is it downshifting by itself or not? Maybe what you mean is that the transmission downshifts with the pedal at WOT, but then it won't SHIFT BACK UP no matter how long you hold the pedal down. If that is the case, I say GOVERNOR. The governor controls WOT shift points. The valve may be sticking, or the weights are binding or hanging up. I would pull the governor and inspect it. Spray it with carburetor cleaner, let it dry, then dip it in some ATF and re install it. The modulator is seeing 0 vacuum with your foot to the floor, the governor determines the up shift point. When you lift your foot, vacuum returns and the modulator over rides the governor.
I think he means it won't upshift back into 3rd untill he releases the gas pedal a hair, then it upshifts, otherwise it holds.
That's what I meant, even though I couldn't articulate it. How do I go about repairing/replacing the governor?
Pretty simple. Get the back end of the car up in the air to minimize fluid loss. On the THM400, the governor is located behind a plate secured by 4 bolts. It's on the passenger side rear of the transmission. After cover removal, the governor will come out with a twist. Then check this link, and click on page 75. Follow the instructions therein. http://books.google.com/books?id=iU...&resnum=2&ved=0CBoQ6AEwAQ#v=onepage&q&f=false
" ... Ok, ok, ok; In my prior 455 Regal, when I would leave out in 2nd and drive down the block @ 50-mph ... and apply the brakes, the Regal would CHIRP the tires and DOWNSHIFT with a hard jerk into 1st on it's own! That was cool to me ... like it was stick-shift:TU:. That was a $75 junkyard TH400 3-speed short-tail transmission. I knew nothing on that tranny (shift kit/year of tranny ... nothing)." WAS THAT NORMAL?????o No:
No. It's not. It should only downshift when your near a stop or the kickdown has been activated under heavy throttle. It's actually very bad for TH400's to downshift when their isn't a lot of throttle input, as the planetaries end up spinning at speeds they should never see, not to mention their being a lack of pressure on the clutch packs. It's a good rule of thumb never to be off the gas in first or second gear on an automatic, allowing engine breaking.
When I said near a stop, I meant down to about 5-10 mph when it downshifts. You shouldn't feel anything at all.
